Commissioning of a Commercial Treatment Planning System Verification Software Package

Purpose: A commercial software package (Mobius3d, Mobius Medical Systems) was acquired for use as an additional QA tool of our current treatment planning system (TPS). The system reads DICOM RT files generated from the TPS and performs an independent dose calculation for comparison to the TPS. This work summarizes our methods for commissioning a system such as this.

Methods: Preliminary comparisons of our TPS and measured data to the QA softwares beam model were done by comparing PDDs and profiles with field sizes ranging from 4x4 to 40x40. Static fields and step and shoot IMRT plans were generated on a homogeneous medium for comparisons of 6x photons. For the homogeneous IMRT cases, ion chamber measurements were compared to the dose calculated in the TPS and in the verification system.

Results: Analysis of PDD data showed that the average PDD error of the verification model (relative to the TPS) was 0.5% compared to our measured data which was 0.1%. The average infield profile error over all field sizes and depths of the TPS to our reference measured data set was 0.3% whereas the verification system relative to the TPS was 1.7%. Simple beam geometries between the TPS and the verification system were 0.8% difference on average. Ion chamber measurements on a homogeneous phantom differed from the TPS on average by 0.5% whereas the verification system was 2%. The results indicate an adjustment in the beam model of the verification system is needed to better match our current beam model/measured data.

Conclusion: Preliminary commissioning results of a commercial QA dose algorithm were completed. Adjustment of the verification softwares beam model is necessary before further testing is done. Further analysis is needed to fully investigate this system to be used clinically as a QA tool of our current TPS.